1. Field of the Invention
This invention relates to a keyboard device for a keyboard instrument, and more particularly to a keyframe of the keyboard instrument, which is disposed on a keybed and used for supporting components, such as keyboard assemblies.
2. Description of the Related Art
Conventionally, as the keyboard device of the conventional keyboard instrument, there has been proposed one disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2003-177739 (see pages 3 and 4, and FIG. 1). This keyboard device includes a keyframe provided on a keybed, and a multiplicity of keys arranged on the keyframe. The keyframe is comprised of a keyframe front, a keyframe center, and a keyframe rear, which extend longitudinally, a pair of left and right keyframe plates, and three inner bunches disposed inward of these, and these components are connected to each other into an assembly and each formed by a molded piece of a synthetic resin.
Further, the keyframe center has a multiplicity of balance rail pins erected thereon, and each balance rail pin is engaged with a balance rail pin hole formed in the center of each key, whereby the keys are swingably supported on the keyframe center. The keyframe front as well has a multiplicity of front rail pins erected thereon, and each front rail pin is engaged with a front rail pin hole formed in the bottom of each key, whereby the keys are prevented from swinging horizontally. According to the keyboard device constructed as above, the keyframe is composed of molded pieces of a synthetic resin, whereby it is possible to easily obtain components having high dimensional accuracy, which makes it unnecessary to perform finishing work on each component. This simplifies the manufacturing process, whereby the manufacturing costs can be reduced. Further, the components has high shape retention against aging and dryness or humidity, which makes it possible to prevent deformation, such as warpage, of the keyboard assembly.
The keyboard device including such a keyframe suffers from the following problem: Since the keyframe is comprised of a plurality of components, as described above, the number of the components is large, and it is necessary to connect the components to each other, which increases the number of assembly steps, resulting in an increase in manufacturing costs. Further, since the keyframe is an assembly of the components, there is a fear of assembly error, and it takes much time to adjust the mounting positions of the keys, etc., which also results in an increase in manufacturing costs.